Mechanistic artefact explanation

One thing about technical artefacts that needs to be explained is how their physical make-up, or structure, enables them to fulfil the behaviour associated with their function, or, more colloquially, how they work. In this paper I develop an account of such explanations based on the familiar notion of mechanistic explanation. To accomplish this, I outline two explanatory strategies that provide two different types of insight into an artefact’s functioning, and show how human action inevitably plays a role in artefact explanation. I then use my own account to criticize other recent work on mechanistic explanation and conclude with some general implications for the philosophy of explanation.Keywords: Artefact; Technical function; Explanation; Levels of explanation; Mechanisms

Religious exclusivism unlimited: JEROEN DE RIDDER

Like David Silver before them, Erik Baldwin and Michael Thune argue that the facts of religious pluralism present an insurmountable challenge to the rationality of basic exclusive religious belief as construed by Reformed Epistemology. I will show that their argument is unsuccessful. First, their claim that the facts of religious pluralism make it necessary for the religious exclusivist to support her exclusive beliefs with significant reasons is one that the reformed epistemologist has the resources to reject. Secondly, they fail to demonstrate that it is impossible for basic religious beliefs to return to their properly basic state after defeaters against them have been defeated. Finally, I consider whether there is perhaps a similar but better argument in the neighbourhood and conclude in the negative. Reformed Epistemology's defence of exclusivism thus remains undefeated

Computational analysis of flow-induced vibrations in fuel rod bundles of next generation nuclear reactors

As our energy demand is ever increasing, new and preferably, cleaner energy sources are being developed. One of the on-going developments are the so-called 4th Generation nuclear reactors, which are significantly (up to 50 times) more efficient than current reactors. In one of the designs of such a reactor the coolant is lead-bismuth eutectic. Due to its high density and the dense packing of fuel rods, flow-induced vibrations might lead to damage. Flow-induced vibrations is a global term to indicate that the vibrations are caused by the interaction of a structural component and a surrounding fluid flow. It can be encountered in a number of fields including nuclear, aeronautical, civil, mechanical and biomedical engineering. This research focuses on the numerical prediction of key parameters of flow-induced vibrations. In contrast to existing approaches, no coefficients have to be tuned in these simulations. The model, which was developed during this research, was shown to accurately predict resonance characteristics (such as eigenfrequencies and damping) of slender structures in axial flow. Moreover, the simulations captured all dynamics including static and dynamic instabilities of a flexible cylinder in axial flow. It was demonstrated that changes in flow pattern were crucial to accurately capture these domains. Even in the stable regime small-amplitude vibrations are occurring, caused by turbulence in the flow. These small-scale vibrations might lead to long-term damage. Those vibrations were successfully predicted by means of Large-Eddy Simulations. The only drawback is that those simulations are very computationally demanding. As the computational power is increasing quickly, these types of simulations are anticipated to play an important role in the design against flow-induced vibrations

Numerical simulation of long and slender cylinders vibrating in axial flow applied to the Myrrha reactor

Flow induced vibrations are an important concern in the design of nuclear reactors. One of the possible designs of the 4th generation nuclear reactors is a lead-cooled fast reactor of which MYYRHA is a prototype. The combination of high liquid density, flow velocity, low pitch-to-diameter ratio and the absence of grid spacers makes this design prone to flow induced vibrations. Although most vibrations are induced by cross flow, axial flow around this slender structure could also induce vibrations. In order to gain insight in the possible vibrations (either induced by cross flow, axial flow or an external excitation) this study examines the change of eigenmodes and frequencies of a bare rod due to the lead-bismuth flow. To do so partitioned simulations of the fluid structure interaction are performed in which the structure is initially perturbed according to an in-air eigenmode

Investigation of confinement effects on zeolite-catalyzed methylation reactions

Catalytic conversion of methanol to light olefins (MTO) over acidic zeolites is currently one of the most prominent alternatives to traditional crude oil cracking processes for the production of ethene and propene. The underlying reaction mechanisms have been under debate for decades, with current insight strongly supporting an indirect mechanism based on the hydrocarbon pool hypothesis: olefin formation is found to occur through repeated methylation and subsequent elimination and/or cracking reactions of organic co-catalysts inside the zeolite pores.[1] Depending on the characteristics of the zeolite material, the predominant hydrocarbon pool species vary from smaller alkenes to bulky polymethylbenzenes.[2] Theoretical studies showed that methylations are generally the rate-determining steps in the olefin producing catalytic cycles; therefore it is of utmost importance to gain an in-depth understanding of these reactions.[3,4] Quantum chemical calculations on extended cluster models that mimic the local environment of the active site were used in this work to model methylation reactions in a selection of zeolite frameworks. Activation barriers and rate constants are then mutually compared to assess the influence of confinement effects caused by different catalyst topologies. The balance between accuracy and computational efficiency signifies this approach as an important step toward routine study of reaction steps in heterogeneous catalysis.[5